The present invention relates to a data transmission apparatus and a data reception apparatus that transmits and receives a data file having a directory structure, and especially relates to a method of effective transmission and reception of a plurality of data files that are to be used simultaneously or successively.
FIG. 26 is a schematic diagram of a data transmission/reception system.
The data transmission/reception system shown in FIG. 26 includes a broadcasting station 901, a broadcasting satellite 902, a portable terminal 903, and a tabletop terminal 904.
Digital data in which a variety of kinds of data such as video, audio, and program information are multiplexed is transmitted over a broadcast wave from the broadcasting station 901. The broadcast wave carrying digital data is relayed by the broadcasting satellite 902 and received by the portable terminal 903 and the tabletop terminal 904. From the received broadcast wave, desired data is extracted and used.
At present MPEG 2 (Moving Picture Coding Experts Group 2) transport stream is mainly used in the data transmission/reception system.
The MPEG 2 is standardized by the ISO/ICE13181. The object carousel (DSM-CC) standardized by the ISO/ICE 13181Extensions for DSM-CC defines the control protocol of data download.
The DSM-CC standard defines a flow control method and a non-flow control method. According to the flow control method, control information is efficiently transmitted and received. As a result, the flow control method is suitable for local data transmission and reception but not suitable for digital broadcasting data transmission and reception, by which the same data is transmitted to many receivers at one time. On the other hand, according to the non-flow control method, control information does not transmitted from a receiver to a sender, so that the non-flow control method is suitable for the data transmission and reception as digital broadcasting.
The non-flow control method defined by the DSM-CC standard includes an data carousel transmission method (DSM-CC-UN) and an object carousel transmission method (DSM-CC-UU). Here the data carousel transmission method includes the object carousel transmission method.
In the data carousel transmission method, data to be transmitted is cyclically transmitted from the sender, and the receiver starts receiving data with almost no wait. Note that the data carousel transmission method is described in chapters 1 to 3 and 7 of ISO/ICE13181-6 in detail.
The object carousel transmission method is a data carousel transmission system in which the standard is expanded as described below so that a file having a directory structure is transmitted.
Data to be transmitted is independent by the module. Each of the modules is composed of a plurality of BIOP messages.
FIG. 27 shows a module composed of a plurality of BIOP messages.
Four different object types, i.e., directory object, file object, stream object, and service gateway (SGW), are defined as the BIOP message. A directory object includes the name of another object directly relating to the directory corresponding to the directory object and the identifier identifies the BIOP message corresponding to the object name. A file object includes file data or bitmap data. A stream object includes the reference to stream data that is transmitted by broadcasting. It can be safely said that a service gateway is the same as a directory object and is a particular directory object that represents the root of a directory structure.
In this specification, the service gateway is considered a kind of directory object and the stream object is considered a kind of file object in the interest of simplicity of the explanation of the present invention.
FIG. 28 shows the definition of directory object.
FIG. 29 shows the definition of file object.
FIG. 30 shows the definition of IOP::IOR.
A BIOP message includes an identifier IOP::IOR (referred to an xe2x80x9cidentifier IORxe2x80x9d in this specification) of a download ID, a module ID, and an object key in its own header. Each of the BIOP messages is identified by the identifier IOR on the receiver side.
FIG. 31 shows the definition of BIOP::Object Location, which is an important element of the identifier IOR in the object carousel transmission method.
FIG. 32 is a schematic diagram of a conventional method for referring to a file message according to the name of the file (a key list) in the object carousel transmission method.
Note that the data carousel transmission method is described in chapters 2, 7, and 9 of ISO/ICE 13181-6, and the object carousel transmission method is described in chapters 4, 5, and 11 of ISO/ICE13181-6.
Showing existing standards, FIGS. 26 to 32 are not explained in detail in this specification.
[Conventional Transmission Apparatus]
FIG. 33 shows the structure of a conventional transmission apparatus for transmitting files having directory structures according to the object carousel transmission method.
A transmission apparatus 100 in FIG. 33 includes an indirect directory message block storage unit 101, an indirect directory message block reading unit 102, a data block storage unit 103, a data block reading unit 104, a multiplexing unit 105, a data transmission unit 106, and an antenna 107.
The indirect directory message block storage unit 101 stores indirect directory message blocks. Note that an indirect directory message block shows the names of the directories and files that directly relate to a directory in the file structure.
The indirect directory message block reading unit 102 reads indirect directory message blocks from the indirect directory message block storage unit 101.
The data block storage unit 103 stores data blocks. Here, one data block includes one file.
The data block reading unit 104 reads data blocks from the data block storage unit 103.
The multiplexing unit 105 multiplexes the read indirect directory message blocks and the read data blocks into digital stream data. More specifically, the multiplexing unit 105 groups the read indirect directory message blocks and the read data blocks into a plurality of modules, gives a different module identifier to each of the modules, gives different object keys to the indirect directory message blocks and data blocks in one module, and divides each of the modules into DDBs, i.e., units of transmission.
The data transmission unit 106 broadcasts the digital stream data according to the object carousel transmission method via the antenna 107.
[Conventional Reception Apparatus]
FIG. 34 shows the structure of a conventional reception apparatus that receives files having directory structures according to the object carousel method.
A reception apparatus 150 shown in FIG. 34 includes a reception antenna 151, a data reception unit 152, a data block selection unit 153, a data separation unit 154, an indirect directory message block selection unit 155, a directory message body obtaining unit 156, an identifier indirect obtaining unit 157, and a key information selection unit 158.
The data reception unit 152 receives data in the object carousel transmission method that is being broadcasted via the reception antenna 151, and restores digital stream data.
The data separation unit 154 extracts indirect directory message blocks and data blocks from the digital stream data. The data separation unit 154 outputs the indirect directory message blocks to the indirect directory message block selection unit 155 and outputs the data blocks to the data block selection unit 154.
The key information selection unit 158 includes a key list buffer 159 for temporarily storing a reference name that is input from a terminal xe2x80x9cAxe2x80x9d. The key information selection unit 158 selects directory names and file names (keys) according to the name of the reference name that the key list buffer 159 stores, and outputs the selected directory names and file names to the identifier indirect obtaining unit 157. For instance, when the reference name is xe2x80x9cxcx9c/abc/def/ghixe2x80x9d, the key information selection unit 158 selects four keys, in the order of xe2x80x9cxcx9cxe2x80x9d, xe2x80x9cabcxe2x80x9d, xe2x80x9cdefxe2x80x9d, and xe2x80x9cghixe2x80x9d. Note that a xe2x80x9cxcx9cxe2x80x9d represents an xe2x80x9cSGW(ServiceGateway)xe2x80x9d, i.e., the root of a directory structure and a xe2x80x9c/xe2x80x9d represents the difference of levels.
The identifier indirect obtaining unit 157 selects an identifier IOR relating to the key that the key information selection unit 158 has output from the indirect directory message body that the directory message body obtaining unit 156 has output, and outputs the identifier IOR to the indirect directory message block selection unit 155 and the data block selection unit 154. Here, when the key is xe2x80x9cxcx9cxe2x80x9d, no indirect directory message body has been output, so that the identifier IOR of the SGW is selected according to a method that is separately defined. Note that the method for selecting the identifier IOR of the SGW has no particular bearing on the principle of the present invention, so that the selection method is not explained.
The indirect directory message block selection unit 155 selects the directory object corresponding to the identifier IOR that the identifier indirect obtaining unit 157 has output from the indirect directory message blocks that the data separation unit 154 has output, and outputs the directory object to the directory message body obtaining unit 156.
The directory message body obtaining unit 156 obtains a BIOP::indirect Directory Message Body in which partial reference names correspond to different identifiers IOR from the directory object, and outputs the BIOP::Directory Message Body to the identifier indirect obtaining unit 157.
The data block selection Unit 153 selects a file object corresponding to the identifier IOR that the identifier indirect obtaining unit 157 has output from the data blocks that the data separation unit 154 has output, and outputs the selected file object from a terminal xe2x80x9cBxe2x80x9d.
The reception apparatus 150 repeats the foregoing process every time a reference name is input from the terminal xe2x80x9cAxe2x80x9d until a file object is output from the terminal xe2x80x9cBxe2x80x9d or the processes for all the keys are completed.
As has been described, in the conventional way of receiving files having directory structures according to the carousel transmission method, it is necessary to repeat the reception of an indirect directory message block and the selection of a directory object the number of times of the directories in order to trace directories until the reception of a target object. As a result, the process is complicated and the period of time required to receive the target object is relatively long. In addition, data is repeatedly transmitted in cycle and the next cycle may be waited for in the process, so that the period of time required to receive the target object may be much longer and unstable.
One solution is proposed to shorten the receiving time. A plurality of data files that are likely to be received in succession (referred to xe2x80x9csimultaneously-used-filesxe2x80x9d in this specification) is transmitted in the same module, and the plurality of simultaneously-used-files are stored in a cache memory with the module when the module is reproduced to shorten the period of time from the reception of one data file to the reception of simultaneously-used-files.
FIG. 35 shows examples of transmitting simultaneously-used-files in one module.
In this method, however, directories still need to be traced. In addition, even when no simultaneously-used-file is stored in a cache memory, the data in the cache memory needs to be kept until the end of the tracing, so that the cache memory is not used effectively.
It is accordingly an object of the present invention to provide a data transmission apparatus, a data reception apparatus, a data transmission method, and a data reception method that effectively transmit and receive a plurality of data files having directory structures to be simultaneously or successively used, a recording medium that stores the data transmission method, and the data reception method, and a recording medium that stores transmission and reception data.
The data reception apparatus according to the present invention is a data reception apparatus that receives a file system having a directory structure and obtains a data file corresponding to a reference name starting from a predetermined directory name, wherein a data block includes a data file and an identifier of the data block, the data reception apparatus that may include: a storage unit for storing a direct directory message body that is used for directly specifying an identifier of a data block corresponding to a reference name according to the reference name; a reference name obtaining unit for obtaining a reference name of a data file to be obtained; a reception unit for receiving multiplexed data into which a plurality of indirect directory message blocks, a plurality of data blocks, and data of at least one direct directory message body have been multiplexed, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory; a separation unit for extracting indirect directory message blocks, data blocks, and data of direct directory message body from the received multiplexed data and outputting the extracted indirect directory message blocks, data blocks, and direct directory message body data; a direct reference unit for outputting, when the direct directory message body stored by the storage unit includes the reference name that the reference name obtaining unit has obtained, a data block identifier that is directly specified according to the reference name according to the direct directory message body; a key information creation unit for separating, when the direct directory message body stored by the storage unit does not include the reference name that the reference name obtaining unit has obtained, a directory name and a file name in the reference name to create key information, and outputting the created key information; an indirect reference unit for outputting, when key information output by the key information creation unit is a predetermined directory name, an identifier of an indirect directory message block of the predetermined directory name; an indirect directory message block selection unit for selecting an indirect directory message block corresponding to the key information from the indirect directory message blocks that the separation unit has output according to the indirect directory message block identifier that the indirect reference unit has output; an indirect directory message body extraction unit for extracting an indirect directory message body from the selected indirect directory message block, wherein when the key information that has been output by the key information creation unit is not a predetermined directory name, the indirect reference unit repeatedly retrieves an identifier corresponding to the key information from the indirect directory message body that the indirect directory message body extraction unit has extracted and outputs the retrieved identifier until a data block identifier is retrieved; a data block selection unit for selecting a data block corresponding to the key information from the data blocks that the separation unit has output according to an identifier that one of the direct reference unit and the indirect reference unit has output and extracting a data file from the selected data block; a direct directory message body selection unit for selecting data of a direct directory message body corresponding to the data block from the data of direct directory message body that the separation unit has output; and an updating unit for storing the selected direct directory message body data in the storage unit.
As a result, when a direct directory message body includes a reference name, the identifier of a data block may be directly identified by the reference name, and when a direct directory message body includes no reference name, the identifier of a data block may be identified by tracing indirect directory message bodies and the direct directory message body may be obtained and stored for the data block that is to be selected later.
Since the direct directory message body for the second data block is stored when the first data block is selected, the identifier of the second data block may be identified directly by the reference name without tracing indirect directory message bodies when the second data block is selected. As a result, the period of time required for reception is shortened.
The data reception apparatus according to the present invention may also be the data reception apparatus, wherein the reception unit receives multiplexed data into which information in a process before selection of the data block and direct directory message body data corresponding to the data block have been multiplexed, and the direct directory message body selection unit selects the direct directory message body data corresponding to the data block in the process before selection of the data block.
As a result, the direct directory message body for the second data block may be obtained in the process of selecting the first data block, so that the amount of work in the process of obtaining the direct directory message body data is reduced.
The data reception apparatus according to the present invention may also be the data reception apparatus, wherein direct directory message body data corresponding to a first data block is information that has been multiplexed into information in a process of selecting the first data block and directly specifies an identifier of a second data block according to a reference name of the second data block that is expected to be successively selected after a selection of the first data block.
As a result, the direct directory message body data for the second data block may be obtained in the process of selecting the first data block
The data reception apparatus according to the present invention may also be the data reception apparatus, wherein the direct directory message body data corresponding to the first data block for a module is multiplexed into a stream that transmits the reproduction information for the module including the first data block, and when receiving the stream that transmits the reproduction information, the direct directory message body selection unit selects direct directory message body data corresponding to the module from the stream.
As a result, the direct directory message body data for the second data block may be obtained when the stream transmitting the reproduction information of the first data block is received.
The data reception apparatus according to the present invention may also be the data reception apparatus, wherein the direct directory message body data corresponding to the first data block is multiplexed into the indirect directory message block that has been selected by the indirect directory message block selection unit when the first data block is selected, and the direct directory message body selection unit selects direct directory message body data from the indirect directory message block that the indirect directory message block selection unit has selected.
As a result, the direct directory message body data for the second data block may be obtained when an indirect directory block is selected for selecting the first data block.
The data transmission apparatus according to the present invention is a data transmission apparatus that transmits a file system having a directory structure that may include: an obtaining unit for obtaining a plurality of indirect directory message blocks, a plurality of data blocks, and at least one direct directory message body, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory, a data block includes an identifier of the data block and a data file, a direct directory message body is used to directly specify an identifier of a data block corresponding to a reference name starting from a predetermined directory name; a multiplexing unit for multiplexing the obtained indirect directory message blocks, the obtained data blocks, and data of the obtained direct directory message body, and creating multiplexed data; and a transmission unit for transmitting the created multiplexed data.
The data transmission apparatus transmits multiplexed data into which a direct directory message body has been multiplexed is transmitted, so that the identifier of a data block may be directly identified by a reference name in a data transmission apparatus that receives the multiplexed data.
As a result, the period of time required for transmission and reception is shortened.
The data transmission apparatus according to the present invention may also be the data transmission apparatus, wherein a direct directory message body is information that is used to directly specify an identifier of a data block corresponding to a reference name of a data file according to the reference name for each of a plurality of data files that are expected to be simultaneously or successively obtained.
As a result, in the data reception apparatus, the identifiers of the corresponding data blocks may be directly identified by the reference names of a plurality of data files that are expected to be simultaneously or successively obtained, so that the identifiers of the data blocks that are expected to be simultaneously or successively obtained may be identified once a direct directory message body is obtained.
The data transmission apparatus according to the present invention may also be the data transmission apparatus, wherein the multiplexing unit multiplexes direct directory message body data into information used for specifying a data block represented by a reference name in the direct directory message body for each reference name in the direct directory message body.
As a result, in the data reception apparatus, the direct directory message body data for the second data block may be obtained in the process of selecting the first data block, so that the amount of work in the process of obtaining the direct directory message body data is reduced.
The data transmission apparatus according to the present invention may also be the data transmission apparatus, wherein the multiplexing unit multiplexes direct directory message body data into a stream used for specifying a module represented by an identifier in the direct directory message body.
As a result, in the data reception apparatus, the direct directory message body data for the second data block may be obtained from the stream that has been reproduced in the process of selecting the first data block, so that the amount of work in the process of obtaining the direct directory message body data is reduced.
The data transmission apparatus according to the present invention may also be the data transmission apparatus, wherein the multiplexing unit multiplexes direct directory message body data into indirect directory message blocks used for specifying a data block represented by a reference name in the direct directory message body for each reference name in the direct directory message body.
As a result, in the data reception apparatus, the direct directory message body data for the second data block may be obtained from the indirect directory message blocks that have been obtained in the process of selecting the first data block, so that the amount of work in the process of obtaining the direct directory message body data is reduced.
The data reception method according to the present invention is a data reception method for receiving a file system having a directory structure and obtaining a data file corresponding to a reference name starting from a predetermined directory name in a data reception apparatus that includes storage unit for storing a direct directory message body used for directly specifying an identifier of a data block corresponding to the reference name according to the reference name, a data block includes a data file and an identifier of the data block, the data reception method may include: a reference name obtaining step for obtaining a reference name of a data file to be obtained; a reception step for receiving multiplexed data into which a plurality of indirect directory message blocks, a plurality of data blocks, and data of at least one direct directory message body have been multiplexed, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory; a separation step for extracting indirect directory message blocks, data blocks, and data of direct directory message body from the received multiplexed data and outputting the extracted indirect directory message blocks, data blocks, and direct directory message body data; a direct reference step for outputting, when the direct directory message body stored in the storage unit includes the reference name that has been obtained at the reference name obtaining step, a data block identifier that is directly specified according to the reference name according to the direct directory message body; a key information creation step for separating, when the direct directory message body stored in the storage unit does not include the reference name that has been obtained at the reference name obtaining step, a directory name and a file name in the reference name to create key information, and outputting the created key information; an indirect reference step for outputting, when key information output at the key information creation step is a predetermined directory name, an identifier of an indirect directory message block of the predetermined directory name; an indirect directory message block selection step for selecting an indirect directory message block corresponding to the key information from the indirect directory message blocks that has been output at the separation step according to the indirect directory message block identifier that has been output at the indirect reference step; an indirect directory message body extraction step for extracting an indirect directory message body from the selected indirect directory message block, wherein when the key information that has been output at the key information creation step is not a predetermined directory name, an identifier corresponding to the key information is repeatedly retrieved from the indirect directory message body that has been extracted at the indirect directory message body extraction step and the retrieved identifier is output until a data block identifier is retrieved at the indirect reference step; a data block selection step for selecting a data block corresponding to the key information from the data blocks that has been output at the separation step according to an identifier that has been output at one of the direct reference step and the indirect reference step and extracting a data file from the selected data block; a direct directory message body selection step for selecting data of a direct directory message body corresponding to the data block from the data of direct directory message body that has been output at the separation step; and an updating step for storing the selected direct directory message body data at the storage step.
As a result, when a direct directory message body includes a reference name, the identifier of a data block may be directly identified by the reference name, and when a direct directory message body includes no reference name, the identifier of a data block may be identified by tracing indirect directory message bodies and the direct directory message body may be obtained and stored for the data block that is to be selected later.
Since the direct directory message body for the second data block is stored when the first data block is selected, the identifier of the second data block may be identified directly by the reference name without tracing indirect directory message bodies when the second data block is selected. As a result, the period of time required for reception is shortened.
The data transmission method according to the present invention is a data transmission method for transmitting a file system having a directory structure that may include: an obtaining step for obtaining a plurality of indirect directory message blocks, a plurality of data blocks, and at least one direct directory message body, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory, a data block includes an identifier of the data block and a data file, a direct directory message body is used to directly specify an identifier of a data block corresponding to a reference name starting from a predetermined directory name; a multiplexing step for multiplexing the obtained indirect directory message blocks, the obtained data blocks, and data of the obtained direct directory message body, and creating multiplexed data; and a transmission step for transmitting the created multiplexed data.
The data transmission apparatus transmits multiplexed data into which a direct directory message body has been multiplexed is transmitted, so that the identifier of a data block may be directly identified by a reference name in a data transmission apparatus that receives the multiplexed data.
As a result, the period of time required for transmission and reception is shortened.
The computer-readable recording medium according to the present invention that records a data reception program is a computer-readable recording medium that records a data reception program for receiving a file system having a directory structure and for obtaining a data file corresponding to a reference name starting from a predetermined directory name in a data reception apparatus that includes storage unit for storing a direct directory message body directly specifying an identifier of a data block corresponding to the reference name according to the reference name, a data block includes a data file and an identifier of the data block, the data reception program has a computer execute steps that may include: a reference name obtaining step for obtaining a reference name of a data file to be obtained; a reception step for receiving multiplexed data into which a plurality of indirect directory message blocks, a plurality of data blocks, and data of at least one direct directory message body have been multiplexed, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory; a separation step for extracting indirect directory message blocks, data blocks, and data of direct directory message body from the received multiplexed data and outputting the extracted indirect directory message blocks, data blocks, and direct directory message body data; a direct reference step for outputting, when the direct directory message body stored in the storage unit includes the reference name that has been obtained at the reference name obtaining step, a data block identifier that is directly specified according to the reference name according to the direct directory message body; a key information creation step for separating, when the direct directory message body stored in the storage unit does not include the reference name that has been obtained at the reference name obtaining step, a directory name and a file name in the reference name to create key information, and outputting the created key information; an indirect reference step for outputting, when key information output at the key information creation step is a predetermined directory name, an identifier of an indirect directory message block of the predetermined directory name; an indirect directory message block selection step for selecting an indirect directory message block corresponding to the key information from the indirect directory message blocks that has been output at the separation step according to the indirect directory message block identifier that has been output at the indirect reference step; an indirect directory message body extraction step for extracting an indirect directory message body from the selected indirect directory message block, wherein when the key information that has been output at the key information creation step is not a predetermined directory name, an identifier corresponding to the key information is repeatedly retrieved from the indirect directory message body that has been extracted at the indirect directory message body extraction step and the retrieved identifier is output until a data block identifier is retrieved at the indirect reference step; a data block selection step for selecting a data block corresponding to the key information from the data blocks that has been output at the separation step according to an identifier that has been output at one of the direct reference step and the indirect reference step and extracting a data file from the selected data block; a direct directory message body selection step for selecting data of a direct directory message body corresponding to the data block from the data of direct directory message body that has been output at the separation step; and an updating step for storing the selected direct directory message body data at the storage step.
As a result, the same effect as the data reception method may be obtained.
The computer-readable recording medium according to the present invention that records a data transmission program is a computer-readable recording medium that records a data transmission program for transmitting a file system having a directory structure, the data transmission program has a computer execute steps that may include: an obtaining step for obtaining a plurality of indirect directory message blocks, a plurality of data blocks, and at least one direct directory message body, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory a data block includes an identifier of the data block and a data file, a direct directory message body is used to directly specify an identifier of a data block corresponding to a reference name starting from a predetermined directory name; a multiplexing step for multiplexing the obtained indirect directory message blocks, the obtained data blocks, and data of the obtained direct directory message body, and creating multiplexed data; and a transmission step for transmitting the created multiplexed data.
As a result, the same effect as the data transmission method may be obtained.
The computer-readable recording medium according to the present invention that records transmission and reception data is a computer-readable recording medium that records transmission and reception data for transmitting and receiving a file system having a directory structure, the transmission and reception data being characterized by multiplexing of (1) a plurality of indirect directory message blocks, an indirect directory message block includes an identifier of the indirect directory message block and an indirect directory message body that is used for specifying an identifier of a data block corresponding to a data file in a first directory according to a name of the data file and is used for specifying an identifier of an indirect directory message block corresponding to a second directory in the first directory according to a name of the second directory for each directory; (2) a plurality of data blocks, a data block includes a data file and an identifier of the data block; and (3) data of at least one direct directory message body that is information used for directly specifying an identifier of a data block corresponding to a reference name starting from a predetermined directory name according to the reference name into the transmission and reception data.
A direct directory message body has been multiplexed into the transmission and reception data, so that the identifier of a data block may be directly identified by a reference name in a data reception apparatus that receives the transmission and reception data.
As a result, the period of time required for transmission and reception is shortened.
The computer-readable recording medium according to the present invention that records transmission and reception data may also be the computer-readable recording medium, wherein direct directory message body data is information that has been multiplexed into information used for specifying the first data block and directly specifies an identifier of a second data block according to a reference name of the second data block that is expected to be successively selected after a selection of the first data block.
The direct directory message body data is multiplexed into information used for identifying the first data block, so that the direct directory message body data may be obtained for the second data block in the process of selecting the first data block in a data reception apparatus that receives the transmission and reception data. As a result, the amount of work in the process of obtaining the direct directory message body data is reduced.